算术操作符重载和关系操作符重载

来源：互联网发布：进销存财务一体软件编辑：程序博客网时间：2024/05/21 09:26
<pre name="code" class="cpp">#include <iostream>#include <string>using namespace std;class Sales_item{public:Sales_item(string &book, const unsigned count, const double amount) :isbn(book), units_sold(count), revenue(amount){}Sales_item& operator+=(const Sales_item&);Sales_item& operator-=(const Sales_item&);friend std::ostream& operator<<(std::ostream&, const Sales_item&);friend bool operator==(const Sales_item&, const Sales_item&); // 关系操作符等于要用友元函数，不等于就不用友元函数，private:string isbn;unsigned units_sold;double revenue;};inline bool operator==(const Sales_item &lhs, const Sales_item &rhs)  // 关系操作符的定义，关系操作符用bool{return lhs.units_sold == rhs.units_sold &&lhs.revenue == rhs.revenue &&lhs.isbn == rhs.isbn;}inline bool operator!=(const Sales_item &lhs, const Sales_item &rhs)  // 不等式操作符不需要进行友元函数定义，{return !(lhs == rhs);}// 这个是函数的声明，Sales_item operator+(const Sales_item&, const Sales_item&);  // 这个是加操作，加的操作不能用引用，它要返回一个新的引用，Sales_item operator-(const Sales_item&, const Sales_item&); // 这个是函数的声明，是减操作，Sales_item& Sales_item::operator+=(const Sales_item& rhs)   // 这个是加等于操作，加等于返回的是一个引用，它修改了当前的对象，{units_sold += rhs.units_sold;revenue += rhs.revenue;return *this;}Sales_item& Sales_item::operator-=(const Sales_item& rhs)  // 这个是函数的定义，{this->units_sold -= rhs.units_sold;   // 这里的this-> 可以省略，this->revenue -= rhs.revenue;return *this;}Sales_item operator+(const Sales_item& lhs, const Sales_item& rhs){Sales_item ret(lhs);ret += rhs;return ret;}Sales_item operator-(const Sales_item& lhs, const Sales_item& rhs){Sales_item ret(lhs);ret += rhs;return ret;}std::ostream& operator<<(std::ostream& out, const Sales_item& s){out << s.isbn << "\t" << s.units_sold << "\t" << s.revenue;return out;}int main(){Sales_item item1(string("0-123-455555-0"), 10, 200.0);Sales_item item2(string("0-123-455555-0"), 2, 50.0);Sales_item result = item1 + item2;cout << result << endl;Sales_item item3(string("0-123-455555-0"), 5, 100);result += item3;cout << result << endl;Sales_item item4(string("0-123-455555-0"), 1, 30);result -= item4;cout << result << endl;Sales_item item5(string("0-123-455555-0"), 10, 200.0);if (item1 == item5){cout << "小崔爱你，" << endl;}if (item1 != item2){cout << "不相同，" << endl;}cout << "xiao cui" << endl;system("pause"); // 暂停，又重新出现一次（请按任意键继续-------）return 0;}
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